Why did the traffic signal light chose these three colors? If is anerythrochloropsia the patient how to do?

Speaking of this problem, we first look at the three colors of the traffic signal light is how to appear. It was in 1868, when the world's first traffic lights appeared in the streets of London. When the signal lamp also only red and green colors, and is far from advanced street lights now, it can only rely on the police station in the signal lamp beside, by pulling a spanner to control the color change. Later, the red and green lights will slowly pop up all over the world. Until 1920, in the United States of Detroit, the yellow signal lights were added in the first time, to remind drivers to signal lights from the green light.

So why these three colors red yellow and green color, rather than the other? This should start from the red. In a variety of colors, red is the most likely to attract people's attention. May be because red is the color of the blood, and red has been given the "alert" the meaning of "ban". So, it is a matter of course that the signal lamp is forbidden to pass. So why is it allowed to pass through the green? This is because at that time, people generally think that red and green, just like black and white, is a pair of complementary colors. Since red represents the prohibition of traffic, then the opposite of the green to indicate that allowed to pass, is the reason of the. The yellow, which is between the red and green colors, is chosen to act as a signal that the traffic lights are to be transformed.

Finally, to tell you a little secret, now traffic lights in most countries actually is not a pure red and pure green, but with the slightly yellowish red and slightly bluish green. This is mainly in order to allow some people with red green color blindness can more easily distinguish the color of the lights.